Oracle Text Application Developer's Guide 10g
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Sample Chapter From Oracle Text Application Developer's Guide 10g
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Text Queries on Document Collections
A text query application enables users to search document collections such as Websites, digital libraries, or document warehouses. Searching is enabled by first
indexing the document collection. The collection is typically static with no
significant change in content after the initial indexing run. Documents can be of any
size and of different formats such as HTML, PDF, or Microsoft Word. These
documents are stored in a document table.
Queries usually consist of words or phrases. Application users can specify logical
combinations of words and phrases using operators such as OR and AND. Other
query operations such as stemming, proximity searching, and wildcarding can be
used to improve the search results.
An important factor for this type of application is retrieving documents that are
relevant to a user query while retrieving as few non-relevant documents as possible.
The most relevant documents must be ranked high in the result list.
The queries for this type of application are best served with a CONTEXT index on
your document table. To query this index, your application uses the SQL CONTAINS
operator in the WHERE clause of a SELECT statement
Flowchart of Text Query Application
A typical text query application on a document collection enables the user to enter aquery. The application issues a CONTAINS query and returns a list, called a hitlist,
of documents that satisfy the query. The results are usually ranked by relevance.
The application enables the user to view one or more documents in the hitlist.
For example, an application might index URLs (HTML files) on the World Wide
Web and provide query capabilities across the set of indexed URLs. Hitlists
returned by the query application are composed of URLs that the user can visit.
Figure 1–2 illustrates the flowchart of how a user interacts with a simple query
application. The figure shows the steps required to enter the query through to
viewing the results. A query application can be modeled according to the following
steps:
1. The user enters a query.
2. The application executes a CONTAINS query.
3. The application presents a hitlist.
4. The user selects document from hitlist.
5. The application presents a document to the user for viewing.